I spotted this spider in my garden (Northern UK). The body is about 20mm long, and it's made a sizeable (50cm) web on a wall.
There's another semi-identical one on a nearby hedge.
What kind is it?
Thanks for the pictures! That's the European Garden Spider (Araneus diadematus)
They are most commonly seen from June to October, but they reach a peak around right now. This species is all over UK, and is widespread in gardens, woodland, and meadows. Here is another picture for reference:
Fun Fact: After laying their eggs in late autumn, the females die and only the eggs make it through winter. Upon hatching, they look quite different from the adults: